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This invention relates to a liner for downhole components. Specifically, this invention is a metal tube having its original uniform shape sufficiently modified by the formation of non-uniform alterations to its shape so that it can be inserted into the bore of a downhole component and then expanded to conform to the interior surface of the downhole component. The shape modifications allow the tube to be expanded beyond its original diameter without rupturing the tube. The application of this invention is useful for any annular component in a production well or a drill string for drilling oil, gas, geothermal wells, or other subterranean excavations.
Provision of a liner in a drill pipe or other downhole component, including well casing, for the purpose of improving the corrosion resistance of the drill pipe or casing and for providing a passageway for electrical conductors and fluid flow is known in the art, as taught by the following references. U.S. Pat. No. 2,379,800, to Hare, incorporated herein by this reference, discloses the use of a protective shield for conductors and coils running along the length of the drill pipe. The shield serves to protect the conductors from abrasion that would be caused by the drilling fluid and other materials passing through the bore of the drill pipe.
U.S. Pat. No. 2,633,414, to Boivinet, incorporated herein by this reference, discloses a liner for an autoclave having folds that allows the liner to be installed into the autoclave. Once the liner is installed, it is expanded against the inside wall of the autoclave using hydraulic pressure.
U.S. Pat. No. 4,012,092, to Godbey, incorporated herein by this reference, discloses an electrical transmission system in a drill string using electrically conductive pipe insulated with a complementary sheath of elastic dielectric liner material. In order to ensure adequate electrical insulation at the ends of each tube, the sheath was slightly longer than its mating tube. The elastic nature of the sheath material enabled it to conform to the geometry of the drill pipe and its joint.
U.S. Pat. No. 2,982,360, to Morton et al., incorporated herein by this reference, discloses a liner for a well casing in a sour well, e.g. a well where hydrogen cracking and embrittlement are believed to be the cause of stress corrosion and failure of metal the well casing. The objective of the disclosure is to provide a liner to protect the casing and other downhole components from the effects of corrosion. A unique feature of this disclosure is that the liner is not bonded to the downhole component, in order to provide some void space between the liner and the component wall. However, it does teach that the metal liner can be expanded against the inside wall of the casing using mechanical or hydraulic pressure.
U.S. Pat. No. 4,095,865, to Denison et al., incorporated herein by this reference, discloses an improved drill pipe for sending an electrical signal along the drill string. The improvement comprises placing the conductor wire in a spiral conduit that is sprung against the inside bore wall of the pipe. The conduit serves to protect the conductor and provides an annular space within the bore for the passage of drilling tools.
U.S. Pat. No. 4,445,734, to Cunningham, incorporated herein by this reference, teaches an electrical conductor or wire segment imbedded within the wall of the liner, which secures the conductor to the pipe wall and protects the conductor from abrasion and contamination caused by the circulating drilling fluid. The liner of the reference is composed of an elastomeric, dielectric material that is bonded to the inner wall of the drill pipe.
U.S. Pat. No. 4,924,949, to Curlett, incorporated herein by this reference, discloses a system of conduits along the pipe wall. The conduits are useful for conveying electrical conductors and fluids to and from the surface during the drilling operation.
U.S. Pat. No. 5,311,661, to Zifferer, incorporated herein by this reference, teaches a method for forming corrugations in the wall of a copper tube. The corrugations are formed by drawing or pushing the tube through a system of dies to reduce the diameter of the end portions and form the corrugations in center portion. Although the disclosure does not anticipate the use of a corrugated liner in drill pipe or other downhole component, the method of forming the corrugations is readily adaptable for that purpose.
U.S. Pat. No. 5,517,843, to Winship, incorporated herein by this reference, discloses a method of making an upset end on metal pipe. The method of the reference teaches that as the end of the metal tube is forged, i.e. upset, the wall thickness of the end of the pipe increases and inside diameter of the pipe is reduced.
An object of the present invention, which is not disclosed or anticipated by the prior art, is to provide a liner that can be adapted for insertion into a downhole component and can accommodate the regular and varying inside diameters found in downhole components. An additional object of the invention is to provide a liner capable of withstanding the dynamic forces and corrosive and abrasive environment associated with drilling and production of oil, gas, geothermal resources, and subterranean excavation.
This invention discloses a liner for downhole annular components comprising an expandable metal tube suitable for conforming to an inside surface of the downhole component, wherein the downhole component may be uniform or non-uniform in cross section and/or material properties. The tube may be formed outside the downhole component and then inserted into the component, or it could be expanded and formed after being inserted into the component. In order to accommodate expansion of the tube and conformity with the interior of the downhole component, the tube is preformed with any of a variety of shape modifications comprising convolutions, corrugations, indentations, and dimples that generally increase the circumferential area of the tube and facilitate expansion of the tube to a desired shape. The metal tube may have generally a circular, square, rectangular, oval, or conic cross section, and the outer surface that interfaces with the inner surface of the downhole component may be polished, roughened, knurled, or coated with an insulating material. Depending on the desired application, the tube may be formed with sufficient force inside the component that it remains in compression against the inside surface wall of the component, or it may be expanded to a lesser diameter. For example, in some cases it may be desirable to expand the tube so that it merely contacts the inside wall of the component, or it may be desirable that the tube be expanded to a diameter that provides an annulus, or other space, between the tube and inside surface of the component. Where an annulus is provided, additional equipment such as pumps, valves, springs, filters, batteries, and electronic circuitry may be installed between the tube and the inside wall of the component. The tube also may be formed over one or more electrical or fiber optic conductors or conduits in order to provide protective passageways for these components.